Dog pens conventionally are either free-standing structures or are built onto existing buildings. In the former case they typically comprise four walls with an access door in one of the walls (referred to herein as the access wall). In the latter case they typically comprise two or three walls with the third and fourth walls being one or two walls existing building, and the access wall being the wall facing the back wall of the pen. If multiple dog pens are constructed side by side, as is often the case with commercial dog boarding kennels, then the side walls extending from the access walls to the back of the dog pens can be shared between adjacent dog pens.
The walls may be solid walls or cage walls of metal mesh or metal bars mounted on an outer frame, or may be part solid and part cage walls. The height of the walls, for reasons of economy, is generally less than the height of an average human adult. The height merely has to be sufficient to prevent a dog from jumping out of the pen, and additional height above that basic minimum is an unnecessary expense. Typically therefore the pen walls are at most 1.75 metres tall. The means that the access door is also at most 1.75 metres tall, and when human adults enter the dog pen for cleaning purposes or to care for the animal within the pen, they must duck under the door lintel which is at or below head height. This can be an irritation when staff in a boarding kennels are constantly bumping their heads on the door lintels. It can even give rise to compensation claims under health and safety legislation. The alternatives so far proposed, however, are expensive. Those alternatives are to have a full height access wall including a full height access door, or to have a full height door and door frame in an otherwise lower access wall. By “full height” in this context there is meant the height of a conventional modern domestic door, which is at least 2.1 metres tall.